1. Field of the Invention
This invention pertains generally to collision avoidance devices for motor vehicles, and more particularly to an apparatus for alerting the driver of a vehicle to the presence of an adjacent vehicle while changing lanes.
2. Description of the Background Art
Knowing the position of other vehicles while driving is often a difficult and inexact operation. So-called "blind spots" exist which can make lane changing operations dangerous if vehicles in adjacent lanes within a critical distance are not detected. In many circumstances drivers "cut off" an adjacent vehicle or otherwise impinge on the right-of-way of the vehicle. Collision, serious bodily injury, or death can occur as a result.
Rear view mirrors have historically been used by a driver in order to determine if the vehicle's path is clear prior to changing lanes, and every person who has ever driven a motor vehicle has, at one time or another, failed to clear his or her blind spot through proper head turning. This is a particular problem for individuals who have a limited range of motion.
Various technological developments have resulted from the need to detect an obstacle in a vehicle's path. For example, U.S. Pat. No. 4,849,731 issued to Melocik on Jul. 18, 1989, discloses a scanning obstacle detection apparatus using a transducer which produces radiant energy and a rotatable reflector which projects the radiant energy outward and redirects reflected energy to the transducer; U.S. Pat. No. 4,766,421 issued to Beggs et al. on Aug. 23, 1988, discloses an object detection apparatus employing electro-optic emitters and detectors; U.S. Pat. No. 4,694,295 issued to Miller et al. on Sep. 15, 1987 discloses a vehicle blind spot detector using infrared and ultrasonic emitters and detectors to indicate the presence of another vehicle and its distance; U.S. Pat. No. 4,626,850 issued to Chey on Dec. 2, 1986, discloses a vehicle detection and collision avoidance apparatus having an acoustic ranging device to detect the presence of other vehicles to the rear of and adjacent to the user's vehicle; and U.S. Pat. No. 3,892,483 issued to Saufferer on Jul. 1, 1975, discloses a distance warning device for vehicles using rearward directed transmitters and a receiver mounted on the front of the vehicle. These devices are deficient, however, in that they not only detect vehicles, but other objects that are in the path of the transmitting and receiving devices.
To further discriminate between vehicles and non-vehicular objects, other devices have employed doppler technology. For example, U.S. Pat. No. 3,662,328 issued to Spivak on May 9, 1972, discloses an apparatus for determining the proximity of moving vehicles using an ultrasonic signal with a frequency proportional to the speed of the transmitting vehicle; U.S. Pat. No. 4,549,181 issued to Tachibana et al. on Oct. 22, 1985, discloses an moving obstacle detection system for a vehicle using a doppler radar device to inform the driver that another vehicle approaches or moves away from the detecting vehicle so that a pedestrian or another vehicle transversing the front of the vehicle is not erroneously detected; and U.S. Pat. No. 4,833,469 issued to David on May 23, 1989, discloses an obstacle proximity detector for moving vehicles and method for use thereof in which an alarm signal is generated when the combination of differential velocity and separation distance between the vehicle and an obstacle reaches an unsafe level. These devices, however, do not screen out objects that are receding above a preset velocity so as to eliminate false signals and ensure detection only of those vehicles which are overtaking, matching the speed of, or receding from the driver's vehicle. As a result, the devices in the foregoing patents could provide false indications of the presence of obstacles. Furthermore, these devices will detect all objects within their range of view regardless of the comparative speed in relation to the driver's vehicle.
Devices heretofore developed for alerting a driver to the presence of an obstacle will alarm from traffic signs, pedestrian benches, and other stationary objects alongside the turning vehicle. A high rate of false alarms renders these devices unusable. Therefore, a need exists for a device which will not only alert the driver of the presence of other vehicles when changing lanes, but alert the driver as to whether the adjacent vehicle is overtaking, matching the speed of, or receding from the driver's vehicle. The present invention satisfies that need.
The foregoing patents reflect the state of the art of which the applicant is aware and are tendered with the view toward discharging applicant's acknowledged duty of candor in disclosing information which may be pertinent in the examination of this application. It is respectfully stipulated, however, that none of these patents teach or render obvious, singly or when considered in combination, applicant's claimed invention.